This invention relates to a watercraft and more particularly to a personal watercraft and an engine exhaust system for such watercraft.
Personal watercraft have enjoyed a substantial amount of success and are quite popular. This type of watercraft is generally recognized as a relatively small watercraft that is designed primarily for operation by a rider who may carry with him no more than two or three additional passengers. This type of watercraft is, as well known, quite sporting in nature.
Because of their small size and high degree of maneuverability, however, there are certain objections to the use of these watercraft on some bodies of water. One of these objections is caused by the fact that this type of watercraft, primarily because of its small size, has a relatively simple exhaust system that does not provide a significant degree of silencing.
This result is mandated primarily by the very compact nature of the watercraft and the relatively small area that is available for exhaust treatment. Because these watercrafts can be utilized on quite small bodies of water, the potential noise may be more objectionable than larger watercraft having unmuffled exhaust systems but which do not operate on these small bodies of water.
This, therefore, a principal object of this invention to provide an improved exhaust system and particularly an exhaust silencing system for personal watercraft.
It is a further object of this invention to provide an improved and compact, yet highly effective silencing system for the exhaust of a personal watercraft.
Generally, personal watercraft may employ one or more expansion chambers which can provide some at relatively limited silencing effect. That is, the conventional exhaust system employed with a personal watercraft does not use a silencing system that embodies a muffler of the type utilized with other engine applications.
The types of mufflers employed in these other applications depend upon the type and acoustical range of silencing to be effected, but they can use a variety of devices such as a plurality of separate expansion chambers interconnected by small interconnecting passages, silencing devices such as Helmholtz resonators or perforated tubes surrounded by an expansion chamber.
It is, therefore, a further object of this invention to provide an improved exhaust system for a personal watercraft that can employ a muffler or silencing device of the noted types.
One difficulty with the incorporation of a muffler or similar silencing device in a personal watercraft, in addition to the space, is the heat that may be generated by such devices. It is, therefore, another object of this invention to provide an improved cooling arrangement for the muffler or silencer of a personal watercraft exhaust system.
The components of the exhaust system also may be relatively bulky in size and can become heavy, particularly if multiple chambers and multiple shells are employed. Because of the small nature of a personal watercraft, therefore, the placement of these components becomes critical so as to maintain the proper balance for the watercraft, particularly when a number of passengers or the seating location of a single rider may vary.
It is, therefore, a still further object of this invention to provide an improved component layout for the exhaust system of a personal watercraft.
In addition to employing expansion chambers and silencing devices, it may also be desirable to provide a catalyst in the exhaust systems for treatment of exhaust gases so as to prevent the emission of unwanted exhaust gas constituents to the atmosphere or to the body of water in which the watercraft is operating. This further complicates the positioning and location of the exhaust system components. This is particularly true if cooling arrangements are employed for the muffler inasmuch as the catalyst should be operated at a relatively high temperature in order to become effective. Thus, the catalyst should not be overcooled.
It is, therefore, a still further object of this invention to provide an improved catalytic and silenced exhaust system for a personal watercraft.
In addition to the aforenoted features, it is also desirable to employ certain sensors in the exhaust system. The placement of the sensors also is important. Furthermore, the sensors should be positioned so that they can be conveniently accessed for servicing.
It is, therefore, yet another object of this invention to provide an improved exhaust system and sensor arrangement for a personal watercraft wherein the sensor components can be conveniently accessed.